Polysaccharides from Nostoc commune Vaucher activate macrophages via NF-κB and AKT/JNK1/2 pathways to suppress colorectal cancer growth in vivo.

Colorectal carcinoma (CRC) is an aggressive malignancy with very limited therapeutic options. As a result, both morbidity and mortality of this malignancy are very high. It is well-established that Nostoc commune Vaucher is a type of healthy food and has been used as a traditional medicine against human cancers. However, the underlying mechanism(s) by which Nostoc commune Vaucher inhibits CRC was never described. Here we reported that polysaccharides from Nostoc commune Vaucher are a potent inhibitor of CRC growth by activating macrophages. Specifically, we purified polysaccharides from Nostoc commune and two fractions of these polysaccharides are able to inhibit the proliferation and growth of five human CRC cell lines with divergent genetic backgrounds. Through activating NF-κB and AKT/JNK1/2 signaling pathways, one fraction of polysaccharides significantly activated macrophages, which was reflected by the enlarged size of macrophages, enhanced phagocytosis and expression of TNF-α and IL-1β. In summary, this study demonstrated that the polysaccharides from Nostoc commune Vaucher are a potent activator of macrophages, which subsequently contributes to the inhibition of CRC.